Depends on what you mean by "observer", but I'd guess you want "watchers". In the "people" area of an issue, there is a "watchers" list - clicking on that will take you to a screen where you can add people to that list (or remove them from it)
You will need to make sure you have "manage watchers" permission in the project.
Badges are a great way to show off community activity, whether you’re a newbie or a Champion.Learn more
@Rachel Wright (Jira Genie), @Billy Poggi (AUG NOVA, DC), and @Dana Jansen (Confluence Queen) are just some of the folks that lead one of the world's most active Atlassian User Group (AUG)....
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs